With the rapid development of display technology, touch screen (Touch Screen Panel) has become popular gradually in life. Currently, the touch screen can be divided into an Add-on-Mode Touch Panel and an In-Cell Touch Panel according to the structure thereof. Among them, the Add-on-Mode Touch Panel is formed by producing a touch screen and a display screen separately and then bonding them together so as to produce a touch panel with a touch function. The Add-on-Mode Touch Panel has the disadvantages such as high production cost, low light transmittance, thicker modules and the like, while the In-Cell Touch Panel has touch electrodes of a touch screen embedded inside a display screen, which decreases the overall thickness of the modules, and significantly reduces the production cost of the touch panel, and gains the favor of the manufacturer of the touch panel.
Meanwhile, as compared with the existing liquid crystal display screen, the display screen with the organic light emitting diodes (OLEDs) is a hot topic of the flat panel display research area, which has the advantages such as a low power, low cost, self-luminous, wide viewing angle and fast response, etc., and is easy to implement color display and a large screen display, suitable to match the IC drivers, and can operate in a wide temperature range. Further, the OLED display has a small volume and light weight, and is easy to implement a flexible display, thus having a broad application prospect. According to different driving modes, OLED can be divided into a passive matrix organic light emitting display (PMOLED) and an active matrix organic light emitting display (AMOLED). Although the PMOLED has the advantages such as a simple producing process and low cost, it has the disadvantages such as crosstalk, high power consumption, low lifespan and the like, thus can not meet the requirement of the large-size high-resolution display. In contrast, AMOLED with TFTs integrated into the panel has advantages such as low driving current as required, low power consumption, long service life, and can meet the requirements of the large size display, such as high-resolution and multiple gray scales.
Different from the Thin film transistor liquid crystal display (TFT-LCD) using a voltage to control the brightness of light-emitting transistors, it is required for OLED to use a stable current to control the brightness of LEDs since the OLED is of the current-driving type. However, due to process technology and the aging of device and other reasons, in the existing 2T1C driving circuit, there is non-uniformity among the threshold voltages of the driving thin film transistors (DTFT) of respective pixels for driving the light emitting diodes, which resulting in variance in the currents flowing through the respective OLEDs even if an identical driving voltage is applied to the gates of the respective driving thin film transistors, thus affecting the display.